1. Field of the Invention
The invention relates to a reactor. The reactor is a passive element that utilizes a coil, and may also be referred to as “an inductor”.
2. Description of Related Art
A reactor is equipped with a core as a magnetic body, and a coil that is wound around the core. In some cases, the reactor is designed to have a bobbin that retains the coil. In many cases, the reactor is often covered with resin for the purpose of being insulated or protected against physical contact with other devices (e.g., Japanese Patent Application Publication No. 2011-249427 (JP-2011-249427 A), Japanese Patent Application Publication No. 2009-246222 (JP-2009-246222 A); and Japanese Utility Model Application Publication No. 05-066950 (JP-05-066950 U).
In a motor drive system of each of electric vehicles including hybrid vehicles, a reactor may be employed in a circuit of a voltage converter or the like. The reactor for electric vehicles allows a large current to flow therethrough, and hence generates a large quantity of heat. Technologies for efficiently cooling the reactor have been desired. In each of Japanese Patent Application Publication No. 2011-249427 (JP-2011-249427 A) and Japanese Patent Application Publication No. 2009-246222 (JP-2009-246222 A), there is disclosed a reactor having coils wound around parallel regions of ring-shaped cores respectively, as a reactor suited for electric vehicles. As a measure against heat, in the art of Japanese Patent Application Publication No. 2011-249427 (JP-2011-249427 A), the cores and the coils are entirely covered with resin, but the coils are partially exposed, and a radiator plate is placed against the coils at the exposed portions of the coils. In the art of Japanese Patent Application Publication No. 2009-246222 (JP-2009-246222 A), when viewed from an axial direction of the coils, the two coils are about half covered with resin with a plane passing two axes of the coils regarded as a border, to secure a strength, and the other halves are exposed to promote heat radiation in the exposed regions.